Hypertrophied palmaris longus muscle, a pseudomass of the forearm: MR appearance--case report and review of the literature.

Magnetic resonance (MR) imaging of the forearm was performed to evaluate a presumed forearm soft-tissue tumor in a 26-year-old man. Sagittal and axial images revealed a mass isointense to muscle just medial to the flexor carpi radialis tendon (in the expected location of the palmaris longus muscle). A diagnosis of hypertrophied palmaris longus muscle was made. The radiologist must be familiar with the MR imaging appearance of normal variants of the palmaris longus muscle, as this can obviate surgery.